Acceleration responsive supplemental fuel supply for variable area venturi carburetor

ABSTRACT

A variable area venturi carburetor has the venturi enlarged by a venturi-like control vacuum actuated servo; during heavy accelerations, the venturi area is mechanically opened wide by overriding the control vacuum to provide greater fuel and air flow than would be provided by movement of the servo by the control vacuum alone at this time, to provide performance.

United States Patent [191 [111 Harrison July 22, 1975 [5 ACCELERATION RESPONSIVE 2215,68? 9/1940 Winkler 4. 261/52 SUPPLEMENTAL FUEL SUPPLY FOR 2,281,176 4/1942 Smith l l l l l l 261/52 VARIABLE AREA VENTURI CARBURETOR 5?; [75] Inventor: Robert S, Harrison, Grosee lle, 3,680,846 8/1972 Bickhaus et a1. l. 261/52 Mich.

- Primary Examiner-Tim R. Miles [73] Asslgmie' Motor Company Dearbom Attorney, Agent, or FirmRobert El McCollum; Keith L. Zerschling [22] Filed: Dec. 26, 1973 [21] Appl No.: 428,525 [57] ABSTRACT A variable area venturi carburetor has the venturi en- [52] Us (3] 261/44 26l/5O 261/52 larged by a venturi-like control vacuum actuated [51] Folzm 9/06 servo; during heavy accelerations the venturi area is [58] Field 44 R 52 mechanically opened wide by overriding the control vacuum to provide greater fuel and air flow than [56] Reierences Cited would be provided by movement of the servo by the UNITED STATES PATENTS 222301 vacuum alone at this time, to provide performl,623,l80 4/1927 Gustafson 261/50 A 2.128.079 8/1938 Dawes 261/50 A 1 Claim 1 Drawmg Figure I I 1 I 1 [/2 D JG 0' 32 r 34 J0 J4 we Q i0 l 4/ L I i 38 22 N w 6 I 42 4a Q CV I 4G I L J2 4 6? z; J29 70 4 ACCELERATION RESPONSIVE SUPPLEMENTAL FUEL SUPPLY FOR VARIABLE AREA VENTURI CARBURETOR This invention relates in general to a motor vehicle carburetor. More particularly, it relates to one having a variable area venturi movable by engine vacuum.

Variable area venturi type carburetors are known in which one or more walls of the venturi move in response to venturi-like vacuum changes to change both fuel flow and airflow capacity. The fuel flow may be inducted from a port in which moves a tapered fuel metering rod attached to a movable wall so that the larger openings provide greater fuel flow.

In a conventional fixed area venturi carburetor, man ifold vacuum serves as the fuel metering signal. During accelerations, the drop in manifold vacuum actuates a power valve or fuel economizer to add extra fuel for performance purposes.

The variable area venturi carburetor described above uses the vacuum signal between the venturi and throttle valve to actuate a servo to open the venturi and withdraw the fuel metering rod to greater fuel delivery setting. No power valve is used. Since venturi-like vacuum changes substantially in proportion to airflow, and therefore, only slowly, any kind of heavy accelerations are likely to provide poor performances due to insuffi cient fuel enrichment.

It is an object of this invention, therefore, to provide a control device for a variable area venturi carburetor that will provide essentially the same increase in fuel flow during heavy engine accelerations as is provided by the power valve of a conventional carburetor.

It is another object of the invention to construct a variable area venturi carburetor with a device that during heavy accelerations will move the fuel metering rod to provide a rich mixture at a faster rate than would be provided by movement of the rod by the venturi-like vacuum signal alone.

It is a further object of the invention to construct a variable area venturi carburetor with vacuum servo means to open the venturi and withdraw a fuel metering rod to greater fuel delivery positions as a function of the changes in venturi-like vacuum, and to provide a device to override the vacuum signal force during heavy accelerations to move the metering rod beyond the position called for by the vacuum signal, to provide additional fuel for better performance.

It is a still further object of the invention to provide a variable area venturi carburetor of the type described above, in which during heavy accelerations short of wide open throttle operation, the device artificially boosts fuel flow until the venturi-like vacuum signal becomes great enough to move the fuel metering rod to a higher fuel flow position than provided by the device.

Other objects, features and advantages of the invention will become more apparent upon reference to the succeeding detailed description thereof, and to the drawing illustrating the preferred embodiment thereof, wherein the single figure illustrates schematically a cross sectional view of a carburetor embodying the invention;

FIG. 1 shows in general a carburetor of the downdraft type on which the air/fuel mixture enrichment device to be described is installed. This particular carburetor is of the variable area venturi type. Although not shown, it has a rectangular induction passage 10, one

wall 12 of which is pivotally movable and has the profile of one-half of a venturi 13. The fixed opposite cooperating wall 14 is formed with a mating profile of a portion of a venturi. The opening thereby comprises a variable area, rectangular venturi in which the airflow capacity varies in proportion to the opening movement of the one wall 12 of the induction passage.

Movable wall 12 is pivotally mounted at 15 on the carburetor body. Pivotally attached to the wall body is a fuel metering rod or needle 16 that is tapered for cooperation with a main fuel metering hole or jet 18. It should be noted that the needle has a controlled taper to provide a richer air/fuel mixture at the larger venturi areas. The jet is located in an aperture in sidewall 14 at approximately the throat or most constricted section of venturi 13. The carburetor body also includes a fuel reservoir 20 with a passage 22 conducting fuel to metering jet 18. A conventional throttle valve 24 is bolted or otherwise fixed on a shaft 25 that is rotatably mounted in the body of the carburetor below venturi 13 to control the flow of air and fuel through the passage.

A spring returned, control vacuum actuated, diaphragm type servo 26 moves wall 12 as a function of changes in venturi-like vacuum upon movement of the throttle valve 24 between idle and wide-open throttle speed positions.

Servo 26 consists of a hollow two piece casting divided into two chambers 28 and 30 by an annular flexible diaphragm 32. The diaphragm is sealingly mounted along its edge in the casting. Chamber 28 is an air chamber, connected to ambient or atmospheric pressure through a passage 34. Chamber 30 is connected to the induction passage in this case at a diverging point 36 of the venturi between the throat portion and the throttle valve by a passage 38 so as to subject chamber 30 to changes in vacuum that varies with airflow but at a different rate than true venturi vacuum. This of course is a matter of choice.

Fixed to one side of diaphragm 32 by a retainer 40 is a plunger or actuator 42 pivotally connected to a shaft portion of movable wall 12. Fixed to the other side of diaphragm 32 is a spring retainer 44 against which is seated a spring 46. The other end of the spring bears against a seat 48 axially adjustable to vary the spring preload.

it will be seen, therefore, that airflow and fuel flow will change proportionally with movements of venturi wall 12 and the throttle valve. Further details of construction and operation of the carburetor per se are not given since they are known and believed to be unnecessary for an understanding of the invention.

Turning now to the invention, throttle valve shaft 25 has a bore 50in which is fixed a pin 52 that projects radially outwardly as shown. A bell crank-like lever 54, or venturi kicker as it may be called, is rotatably mounted on shaft 25.

The kicker 54 has an actuating finger portion 56 projecting from a sleeve-like mounting or bearing portion 58. The actuating portion 56 is adapted to engage a screw 59 that is adjustably mounted on the depending mounting leg 60 of wall 12. The kicker 54 also has a spring reaction portion 61 and lug 62, for a purpose to be described.

The bearing portion 58 has an arcuate cutaway or recess 64 defining a pair of abutments 66 and 68. The abutments lie in the path or arcuate movement of pin 52 to be engaged by the pin after it has taken up the lost motion provided by recess 64. Subsequent movement of pin 52 then will rotate lever 54 in the same direction.

A spring 70 normally biases lever 54 in a counterclockwise or closed throttle valve direction until lug 62 abuts against the bottom wall of a shell 72 enclosing the device.

In operation, the throttle valve shaft 25 is free to rotate through off idle throttle valve positions without movement of kicker 54. During this movement, opening of throttle valve 24 increases the airflow through the induction passage and thus the control vacuum to servo chamber 30. The venturi then is slowly pulled open by the servo from the idle speed position, with the metering rod 16 being withdrawn to a larger fuel supply opening.

In the event the throttle valve now is opened to a heavy acceleration position short of wide open throttle attitude, the control vacuum, like the airflow, rises only gradually, as is the characteristic of changes in venturi vacuum. This would not open the venturi sufficiently to relieve the airflow restriction nor would it withdraw the metering rod to a position providing the performance fuel quantity desired. With the kicker 54 of the invention, however, the venturi is opened mechanically by the kicker engaging the pivotally movable venturi wall leg 60 and physically moving it. This opens the venturi and withdraws the metering rod 16 to a position providing more fuel, in a manner similar to the result provided by a power valve in a conventional fixed area venturi carburetor.

The kicker thus overrides the control vacuum in passage 38 to open the venturi wider. This overriding feature will be maintained until the rise in venturi-like or control vacuum moving servo 26 catches up to the position the venturi wall has been moved by the kicker 54. At that point, further buildup in control vacuum, with sustained depression (opening) of the throttle valve, will then permit the servo 26 to move the venturi open further and move leg 60 away from kicker 54. Thus, the control vacuum will regain control of the movement of wall 12.

Release of the throttle valve will permit return spring 70 to rotate kicker 54 away from venturi mounting leg 60 to the inoperative position shown.

The same initial operation will occur when the throttle shaft is rotated to a wide open throttle position. The kicker then will rotate the venturi mount leg 60 to a maximum venturi open position for maximum fuel flow, and again override the effect of the control vacuum acting on servo 26. In this case, however, the control vacuum buildup will eventually rise to the point where it is sufficient to cause the servo to move the venturi open to the same setting. Since the venturi is already wide open, however, control vacuum at this time is not able to open it wider. If the throttle valve is relaxed, then the higher control vacuum, is such be the case, can regain control of movement of the venturi, as described previously.

From the foregoing, therefore, it will be seen that the invention provides a device to artificially boost the fuel flow quantity to obtain richer mixture performance during engine accelerations.

While the invention has been shown and described in its preferred embodiment, it will be clear to those skilled in the arts to which it pertains, that many changes and modifications may be made thereto without departing from the scope of the invention.

I claim:

1. A carburetor variable venturi control device for use with a carburetor having an induction passage open to air essentially at atmospheric pressure at one end and adapted to be connected to an internal combustion engine intake manifold at the opposite end, the induction passage containing a movable variable area venturi, defined by at least one movable partial venturishaped wall cooperating with a number of matingly venturi-shaped stationary walls together defining a venturi, the movable wall being movable to vary the crosssectional area of the venturi, a variable area fuel port adjacent the venturi whereby fuel is inducted into the passage during airflow through the venturi, tapered fuel metering means secured to the movable wall and cooperating with the fuel port to vary the fuel port area as a function of the change in venturi area to change fuel flow concurrent with airflow capacity changes, a throttle valve mounted for a rotative movement across the passage between closed and fully open positions to control airflow capacity through the passage, control means to simultaneously vary the area of the venturi and the fuel port to vary both airflow and fuel flow, including vacuum servo means operably connected to the venturi movable wall to move the same and responsive to rises in carburetor venturi-like vacuum acting thereon for enlarging the venturi and fuel port, and other means operable in response to a predetermined movement of the throttle valve to increase fuel flow by overriding the action of the venturi-like vacuum servo means and mechanically moving the venturi movable wall to a larger venturi area position than the position to which the venturi movable wall normally would be moved by the level of venturi-like vacuum acting on the servo means, to increase fuel flow and airflow capacity beyond the level that would be provided by movement of the wall by the level of venturi-like vacuum prevalent for the same position of the throttle valve and engine speed and load conditions, the other means comprising a lever rotatably mounted on the throttle valve with a lost motion connection therebetween, the lever being operably engagable with the venturi wall to move the same after a predetermined initial opening move ment of the throttle valve, the lost motion connection including a shaft mounting the throttle valve, pin means projecting from the shaft, the lever having an abutment portion in the path of opening throttle valve movement of the pin means to be engaged by the second means, the portion being spaced from the pin means in the closed position of the throttle valve, and spring means biasing the lever abutment portion towards the pin means away from the venturi movable portion. 

1. A CARBURETOR VARIABLE VENTURI CONTROL DEVICE FOR USE WITH A CARBURETOR HAVING AN INDUCTION PASSAGE OPEN TO AIR ESSENTIALLY AT ATMOSPHERE PRESSURE AT ONE END AND ADAPTED TO BE CONNECTED TO AN INTERNAL COMBUSTION ENGINE INTAKE MANIFOLD AT THE OPPOSITE END, THE INDUCTION PASSAGE CONTAINING A MOVABLE VARIBLE AREA VENTURI, DEFINED BY AT LEAST ONE MOVABLE PARTIAL VENTURI-SHAPED WALL COOPERATING WITH A NUMBER OF MATINGLY VENTURI-SHAPED STATIONARY WALLS TOGETHER DEFINING A VWENTURI, THE MOVABLE WALL BEING MOVABLE TO VARY THE CROSS-SECTIONAL AREA OF THE VENTURI, A VARIABLE AREA FUEL PORT ADJACENT TH VENTURI WHEREBY FUEL IS INDUCTED INTO THE PASSAGE DURING AIRFLOW THROUGH THE VENTURI, TAPERED FUEL METERING MEANS SECURED TO THE MOVABLE WALL AND COOPERATING THE FUEL PORT TO VARY THE FUEL PORT AREA AS FUNCTION OF THE CHANGE IN VENTURI AREA TO CHANGE FUEL FLOW CONCURRENT WITH AIRFLOW CAPACITY CHANGES, A THROTTLE VALVE MOUNTED FOR A ROTATIIVE MOVEMENT ACROSS THE PASSAGE BETWEEN CLOSED AND FULLY OPENED POSITIONS TO CONTROL AIRFLOW CAPACITY THROUGH THE PASSAGE, CONTROL MEANS TO SIMULTANEOUSLY VARY THE ARE OF THE VENTURI AND THE FUEL PORT TO VARY BOTH AIRFLOW AND FUEL FLOW, INCLUDING VACUUM SERVO MEANS OPERABLY CONNECTED TO THE VENTURI MOVABLE WALL TO MOVE THE SAME AND RESPONSIVE TO RISES IN CARBURETOR VENTURI-LIKE VACUMM ACTING THEREON FOR ENLARGING THE VENTURI AND FUEL PORT, AND OTHER MEANS OPERABLE IN RESPONSE TO A PREDETERMINED MOVEMENT OF THE THROTTLE VALVE TO INREASE FUEL FLOW BY OVERRIDING THE ACTION OF THE VENTURI-LIKE VACUUM SERVO MEANS AND MECHANICALLY MOVING THE VENTURI MOVABLE WALL TO A LARGER VENTURI AREA POSITION THAN THE POSITON TO WHICH THE VENTURI MOVABLE WALL NORMALLY WOULD BE MOVED BY THE LEVEL OF VENTURI-LIKE VACUUM ACTING ON THE SERVO MEANS, TO INCREASE FUEL FLOW AND AIRFLOW CAPACITY BEYOND THE LEVEL THAT WOULD BE PROVIDED BY MOVEMENT OF THE WALL BY THE LEVEL OF VENTURI-LIKE VACUUM PERVALENT FOR THE SAME POSITION OF THE THROTTLE VALVE AND ENGINE SPEED AND LOAD CONDITIONS, THE OTHER MEANS COMPRISING A LEVER ROTATABLY MOUNTED ON THE THROTTLE VALVE WITH A LOST MOTION CONNECTION THEREBETWEEN, THE LEVER BEING OPERABLY ENGAGABLE WITH THE VENTURI WALL TO MOVE THE SAME AFTER A PREDETERMINED INITIAL OPENING MOVEMENT OF THE THROTTLE VALVE, THE LOST MOTION CONNECTION INCLUDING A SHAFT MOUNTING THE THROTTLE VALVE, PIN MEANS PROJECTING FROM THE SHAFT, THE LEVER HAVING AN ABUTMENT PORTION IN THE PATH OF OPENING THROTTLE VALVE MOVEMENT OF THE PIN MEANS TO BE ENGAGED BY THE SECOND MEANS, THE PORTION BEING SPACED FORM THE PIN MEANS IN THE CLOSED POSITION OF THE THROTTLE VALVE, AND SPRING MEANS BIASING THE LEVER ABUTMENT PORTION TOWARDS THE PIN MEANS AWAY FROM THE VENTURI MOVABLE PORTION. 